Method and apparatus for coin selection



March 19, 1968 NL. KUSTERS ET AL 3,373,856

METHOD AND APPARATUS FOR COIN SELECTION Filed May 23, 1966 s Sheets-Shet1 INPUT" CHUTE REJECTED ACCEPTED COINS OR COINS SLUGS F! G. l

OSCILLATOR 26 //v\/- ram 24 SELECTION NOEBE/QT 1. K01 rem CIRCUITSMALCOLM March 19, 1968 N. 1.. KUSTERS ET AL 3,373,856

METHOD AND APPARATUS FOR COIN SELECTION Filed May 23, 1966 5Sheets-Sheet 2 ':S\\,\26 EL C \fZ PC ZgA J 22 OSCILLATOR SELECTIONClRCUlTS SET POINTi 32 r 23 28 PEAK LOGIC DETECTOR cmcun' RELAY- 4 BDRIVER RELAY OSCILLATOR RECT'F'ER ism POINT AND NOT PEAK. DETECTOR AFIG. 6

//v vE/v rores March 19, 1968 1 us s ET AL 3,373,856

METHOD AND APPARATUS FOR com SELECTION Filed May 25, 1966 a Sheets-Sheet:5

Ala/98547 L. Mare-ks MAL AcrrAer/A/ United States Patent 12 Claims. in.194-100 FOR This invention relates to coin selector mechanisms and moreparticularly to a method and apparatus capable of detecting andrejecting spurious or counterfeit coins or slugs and accepting as valid,coins that may be made of either a non-magnetic metal or alloy havingknown electrical characteristics or a magnetic metal or alloy havingknown electro-magnetic characteristics.

At the present time the coins of the larger denominations of mostcountries are made of a metal alloy the major constituent of which issilver. For example, the US. 25-cent piece is 90 silver and the Canadian25-cent piece is 80% silver. These coins are used not only for ordinarymoney transactions but also quite widely in coinoperated vendingmachines. The coin-operated mechanisms of the more sophisticated type.usually incorporate coin testing devices so that spurious coins, tokens,slugs, or other objects not conforming to a given specification will berejected. The coin testing devices presently used normally test not onlyweight and size of the coins inserted but also an electricalcharacteristic such as resistance, capacitance, or the eddy-currentbraking action on the coin as it rolls past a permanent magnet. Thislatter method is used quite widely and is quite effective andsatisfactory for testing coins made of non-magnetic material such assilver. If coins with ferromagnetic properties are inserted, they arestrongly attracted to the permanent magnet and are rejected by theselector mechanism.

At the present time there is a worldwide shortage of silver and manycountries are studying the desirability and possibility of issuing coinswhich contain either no or only a minor proportion of silver with theother proportion being of nickel, copper, iron, steel, or other metals.The United States Government has announced that they will begin issuingZS-cent pieces and lO-cent pieces using a sandwich style coin with thefaces composed of a copper-nickel alloy plus a core of pure copper. Itis claimed that these coins are completely compatible with the oldsilver coins in that they have the correct electrical properties tooperate the large numbers of coin-operated vending machines.

Several countries including Canada would like to issue coins with alarger base metal content. Up until now there has been no known way ofmaking these coins of solid metal or alloy with the correct electricalproperties to make them compatible with the old silver coins in coinselector mechanisms. The sandwich type coin provides difficulties inmanufacture and an undesirable appearance from a metal or alloy havingferromagnetic properties.

It is another object of the invention to provide a coin testing methodand apparatus that will be readily adaptable to present coin operatedvending machines and that Patented Mar. 19, 1968 will be compatible inthat it will accept coins presently in use and any new types of coinsthat might be decided upon by a country or state. 1

These and other objects of the invention are achieved by passing analternating magnetic field through the coin and measuring theattenuation of the magnetic field caused by the coin.

Applicants have found that if a magnetic field is passed through a coin,the attenuation of the magnetic field caused by the coin can be measuredand used as the criterion for the acceptance of the validity of thecoin. It follows from this that a coin selector mechanism can bedesigned and built for accepting as valid a coin of known properties anddiscriminating against all others provided the parameters of theselector mechanism such as operating frequency and geometry of themagnetic circuitry are properly selected. In addition, applicants havefound that the attenuation in a non-magnetic material varies with thefrequency of the alternating magnetic field but in the case of amagnetic material it is nearly independent of frequency. It follows fromthis that if the operating frequency is properly chosen, the sameattenuation can be obtained with the present silver coins and coins madeof a material having some ferromagnetic properties.

According to the invention a coin testing mechanism is provided whereinthe coin under test is inserted in the field generated by a magneticdevice positioned on one side of the coin and the voltage induced in asuitable pickup device positioned on the opposite side of the coin ismeasured. The frequency of input voltage to the magnetic circuit, andthe positions of the driving device, pickup device, and coin are chosensuch that the variation of signal due to eddy currents in a coin made ofnon-magnetic material, e.g. silver would be or could be adjusted to besubstantially equal to the variation of signal due to the presence of acoin made of magnetic material, e.g. nickel, stainless steel. p

According to another more versatile aspect of the invention a cointesting apparatus is provided wherein the coin under test is inserted inthe field induced by a magnetic driver device placed on one side of thecoin so that it attenuates the voltage generated in a suitable pick-updevice placed on the opposite side of the coin. In this case a pick-upcoil surrounds the coin under test and has a voltage induced in it bythe magnetic flux passing mainly through the coin and not across thecoin to the pick-up device. The frequency of the input voltage, thepositions of the driver device, the pick-up device, and the coil aroundthe coin are chosen such that the signal obtained by adding the signalfrom the pick-up device and the coil around the coin would besubstantially the same if the coin is made from a non-magnetic materialor a magnetic material. v

In drawings which illustrate an embodiment of themvention, l

FIGURE 1 is a schematic view ofa coin selector mechanism according tothe invention, I i

FIGURE 2 is a cross-section of a portion of the device of FIGURE 1,

FIGURE 3 is a plan view in cross-section of sensing device,

FIGURE 4 is similar to FIGURE 2 but shows an additional winding thatencircles the coin as-it passes through the sensing station,

FIGURE 5 is a plan view in cross-section of the .coin sensing deviceshowing the additional winding,

FIGURE 6 is a block diagram of the electronic circuitry of the device,

FIGURE 7 is a schematic view of the magnetic field producing anddetecting circuitry, and

the coin 3 FIGURE 8 is a graph of experimental results showing therelationship of frequency to response of some typical coin materials.

Referring to FIGURE 1 a coin selector mechanism is shown in somewhatschematic form. A plate structure 10 .carries an input chute 11 whichleads to a coin sizing and weighing mechanism 12. This type of device iswell known and in use at present and therefore forms no direct part ofthe present invention. After the coin is accepted by device 12 is wouldpass or roll down an inclined chute 13 past a coin sensing station 14which will be described in more detail below. The coin then passes aselector gate 15 hinged at 16. Gate 15 is operated by a solenoid orrelay (not shown) which in turn is connected to the operating circuitry.If the coin is to be accepted gate 15 pivots to allow the coin to passstraight down chute 17. If to be rejected, the gate pivots to allow thecoin to go down chute 18.

FIGURE 2 shows a coin 19 passing down inclined chute 20 past a sensingstation made up of a magnetic core 21 energized by means of a winding 22connected to an oscillator 23. FIGURE 3 shows the sensing station inmore detail. The coin 19 (seen here from the top) passes between thepole faces of a magnetic field producing core 21. The frequency ofoscillator 23 is pro-determined and pre-set such that an alternatingmagnetic field of known frequency is set up. An alternating voltage isinduced in detection winding on magnetic core 24 and is applied to theselection circuits 26. The amplitude of the voltage produced isdependent on the attenuation in the magnetic field between the polefaces of cores 21 and 24. If a coin is positioned between these polefaces the attenuation varies with the size, shape, and electricalproperties of the coin.

FIGURE 4 and FIGURE 5 are similar to FIGURES 2 and 3 but show anadditional winding 27 which is positioned to encircle the coin as itpasses through the sensing station. This winding is connected in serieswith detection winding 25 and therefore adds a voltage related to themagnetic flux passing through the coin and not reaching core 24. Thiswinding is not necessary in all cases but adds flexibility to theinvention in that the device may be designed to accept certain types ofcoins that it might otherwise be difiicult to accommodate due to theirelectrical and magnetic characteristics.

FIGURE 6 shows the selection circuitry in block form. The coin 19 ispositioned between energizing circuitry 22 and detection winding 25.By-pass winding 27 may be connected in at points X and Y if desired. Thealternating voltage induced in detection winding 25 is rectified inrectifier 28 and the DC voltage obtained is applied to a peak detector(A) 30 which gives an output signal if the voltage exceeds apredetermined and pre-set level and also to a peak detector (B) 31 whichgives an output signal if the voltage exceeds another pre-determined andpre-set level. The output signals from the detectors 30 and 31 areapplied to a logic gate 32 which gives an output only if there is asignal from detector 31 and not from detector 30. It will be realizedthat an output is obtained only if the voltage level induced indetection winding-lies between the two pre-set levels and therefore apass band of pre-determined size can be established in the system. Theoutput from logic gate 32 is applied to a relay driver 33 which operatesa relay 34 when energized. The relay is connected to operate selectiongate 15 (see FIG- URE 1) in such a way as to send a coin down chute 17if and only if the correct operating signal is obtained.

FIGURE 7 shows the magnetic circuitry and some of the parameters thatmight be considered in the design of the device or that could bearranged to be varied as required. A coin 19 of diameter C is betweenthe pole faces of magnetic cores 38 and 39 of pole spacing S and inwhich the gap spacing is G. In a working device this gap spacing couldbe made adjustable to meet varying conditions by means of a suitablescrew adjustment.

FIGURE 8 is a graph of results obtained from an experimental set-upwherein different types and sizes of coins were tested. Voltage response(actually attenuation caused by the coins) is plotted against frequency.It will be seen that in coins that are made of non-magnetic material(copper, silver, aluminum, brass) the response is frequency dependent.For magnetic materials (steel) the response is generally independent offrequency. Nickel would be similar to steel but the Canadian S-centpiece tested is made of nickel that has conductive and magneticproperties and therefore has a curve that lies between the curves forthe other materials. The important point to be gained from this graph isthat for any two types of coin materials there is a frequency at whichthe curves cross or in other words at which the signal response is thesame. From this it follows that for a coin made of magnetic material andanother coin made of a non-magnetic material, a frequency can bedetermined that will give the same voltage response and a selectingdevice can be designed and built according to the invention that willfind both types of coins acceptable.

In addition to the operating frequency the relative response betweenmagnetic and non-magnetic materials is affected by the geometry of themagnetic devices, e.g. pole spacing and air gap. A third method ofvarying the response for magnetic coin materials is to place a coilaround the coin when it is in the detecting position. This coil wouldmeasure the by-pass flux, that is, the flux that passes down the coinand does not reach the core on the opposite side of the coin (see coil36 of FIGURE 7). The voltage induced in this coil may be added to thevoltage obtained from the detection winding. In this way the responsecurve of a coin of a magnetic material may be altered and in some casesthis may be necessary or desirable. A magnetic shunt 40 (FIGURE 7) maybe used if necessary to by-pass a portion of the flux through bypasscoil 36. This may be desirable when operating with certain coins. Itwill be realized that there are various parameters that can be designedinto the apparatus or adjusted after the apparatus is built which giveflexibility and wide capability to a selector mechanism built accordin gto this invention.

In the above description and in the claims that follow the method andapparatus has been described in terms of a coin selector mechanism. Itshould be pointed out that applicants consider the word coin in thiscontext applies not only to the official coinage of a country or statebut also to tokens, slugs, and other objects of this nature and also tokey-like devices that might be used in automated merchandise processingsystems.

What is claimed is:

1. A method of testing coins comprising passing an alternating magneticfield through the coin to be tested, measuring the variation in thefield strength due to the coin, and applying the measurement so obtainedto discrimination means such that coins causing a variation in fieldstrength that lie within a pre-determined range are found to beacceptable and all others rejected.

2. A method of testing coins comprising passing an alternating magneticfield through the coin to be tested and measuring the variation in thefield strength due to the coin, the frequency of the alternatingmagnetic field being chosen such that the said variation in fieldstrength will be substantially the same for a coin made of a magneticmaterial having predetermined characteristics and a coin made ofnon-magnetic material having pre-determined characteristics.

3. A method of testing coins comprising generating analternatingmagnetic field on one side of the coin to be tested,obtaining an electrical signal related to the field strength at aposition on the opposite side of the coin, and applying the signal to agating device adapted to operate to send the coin to an accept locationwhen the signal lies within a pre-determined range.

4. A method of testing coins comprising generating an alternatingmagnetic field on one side of the coin to be tested, obtaining anelectrical signal related to the field strength at a position on theopposite side of the coin, and applying the signal to a gating deviceadapted to operate to send the coin to an accept location when thesignal lies within a predetermined range, the frequency of thealternating magnetic field being chosen such that the signal obtainedwill be substantially the same for a coin made of a magnetic materialhaving pre-determined characteristics and a coin made of non-magneticmaterial having pre-determined characteristics.

5. A coin selector mechanism comprising:

(a) means for producing an alternating magnetic field positioned on oneside of the coin to be tested,

(b) magnetic pick-up means positioned on the opposite side of the saidcoin to obtain an output signal, the amplitude of which is related tothe attenuation caused 'by the coin to the magnetic field as it passesfrom the means for producing an alternating magnetic field to thepick-up means,

(c) discriminator means connected to said pick-up means adapted todiscriminate between a relatively narrow pre-determined signal band andall other signal levels, and

(d) a coin selector actuating mechanism operatively connected to saiddiscriminator means adapted to direct the test coin to an acceptlocation when the signal level received in the discriminator lies withinthe pre-set band and to a reject location when the signal level liesoutside the pre-set band.

6. A coin selector mechanism comprising:

(a) means for producing an alternating magnetic field positioned on oneside of the coin to be tested,

(b) magnetic pick-up means positioned on the opposite side of the saidcoin to obtain an output signal, the amplitude of which is related tothe attenuation caused by the coin to the magnetic field as it passesfrom the means for producing an alternating magnetic field to thepick-up means,

() discriminator means connected to said pick-up means adapted todiscriminate between a relatively narrow pre-determined signal band andall other signal levels, and

(d) a coin selector actuating mechanism operatively connected to saiddiscriminator means adapted to direct the test coin to an acceptlocation when the signal level received in the discriminator lies withinthe pre-set band and to a reject location when the signal level liesoutside the pre-set band,

(e) the frequency of operation of the said means for producing analternating magnetic field being chosen such that the attenuation of theelectrical signal between the said means for producing the alternatingmagnetic field and the said magnetic pick-up means is substantially thesame for a coin made of non-magnetic material and a coin made of a metalor alloy having at least some ferromagnetic properties.

7. A coin selector mechanism as in claim 5 wherein the core positionedadjacent the opposite side of the coin from that of the means forproducing an alternating magnetic field.

9. A coin selector mechanism as in claim 5 wherein coil means surroundsthe coin to be tested and is adapted to produce a signal related to themagnetic flux passing through the coin and not reaching said magneticpick-up means, said signal being added to the signal obtained by thesaid magnetic pick-up means.

10. A coin selector mechanism as in claim 5 wherein the said means forproducing an alternating magnetic field is a coil wound on a U-shapedcore positioned on one side, of the coin to be tested, said core havinga magnetic shunt positioned in relation to it such that a portion of theflux passing through the said core is by-passed and does not passthrough the said coin.

11. A coin selector mechanism comprising:

(a) an oscillator,

(b) coil means for producing an alternating magnetic field connected tosaid oscillator and positioned adjacent one face of the coin to betested,

(c) magnetic coil pick-up means positioned adjacent the opposite face ofthe coin to be tested and adapted to provide an output voltage signal,the amplitude of which is related to the attenuation caused by the cointo the magnetic field strength between said coil means and said magneticpick-up means, i

(d) rectifier means connected to said pick-up means to change saidoutput voltage to a DC. voltage level,

(e) a first detector connected to the output of said rectifier andadapted to give an output signal when the said DC. voltage level exceedsa first pre-set voltage level,

(f) a second detector connected to the output of said rectifier andadapted to give an output signal when the said DC. voltage level exceedsa second pre-set voltage level, said first and second pre-set voltagelevels defining a voltage level band,

(g) a logic gate connected to the outputs of said first and seconddetectors, said gate giving an output signal when the said D.C. levelfalls within the said voltage level band,

(h) a relay driver circuit connected to the output of said logic gateand adapted to operate a relay, and

(i) mechanical gating means connected to said relay and adapted todirect the coin after test either to an accept location or a rejectlocation depending on whether the said output DC. voltage level lieswithin or without the defined voltage level band.

12. A coin selector mechanism as in claim 11 wherein the frequency ofoperation of the said oscillator is chosen such that the attenuation tothe magnetic field strength will be substantially the same for a coinmade of nonmagnetic material and a coin made of a metal or alloy havingmagnetic properties.

References Cited UNITED STATES PATENTS 2,329,810 9/1943 Zuschlag 2098l.12,642,974 6/1953 Ogle 194-l00 3,020,472 2/ 1962 Cauley 209-11183,059,749 10/1962 Zinke 194l00 SAMUEL F. COLEMAN, Primary Examiner.

1. A METHOD OF TESTING COINS COMPRISING PASSING AN ALTERNATING MAGNETIC FIELD THROUGH THE COIN TO BE TESTED, MEASURING THE VARIATION IN THE FIELD STRENGTH DUE TO THE COIN, AND APPLYING THE MEASUREMENT SO OBTAINED TO DISCRIMINATION MEANS SUCH THAT COINS CAUSING A VARIATION IN FIELD STRENGTH THAT LIE WITHIN A PRE-DETERMINED RANGE ARE FOUND TO BE ACCEPTABLE AND ALL OTHERS REJECTED. 